Gorilla Doctors

Shinda Group in November 2008: The silverback Shinda sleeps in the background with female Pasika and black back Wageni in the foreground.

Forgive me for not blogging over the last few weeks, and for returning with a sad report about the deaths of several gorillas.  We didn’t have the opportunity to treat these individuals, but we did do post mortem exams on three of the four.  If the rule-of-threes holds, the good news is we won’t have another dead gorilla for a while.

The first two deaths were newborns.  The day had started off with great news.  Veronica, the coordinator for Karisoke Research Center, called to say twins had been born in Pablo Group!  The babies looked healthy and strong (only one set of twins has survived since monitoring of the mountain gorillas began years ago.  See 2007 blog post about Mugeni in Kwitonda Group – here’s the link).  Then she delivered the bad news: the twins’ mother had only recently rejoined the group.  I gasped, and asked about Cantsby, the lead silverback, wondering why he hadn’t killed them.  Veronica said he seemed calm. But when she called back an hour later, I almost didn’t need to hear the words over the phone—her voice was enough.  At least it had happened before everyone had time to get excited about the birth of the twins.

Later that day, the trackers were able to recover one of the infants so that we could do a routine post mortem analysis.  It was a female with a crushed skull (sorry to be so graphic).  We guessed that she had died instantly.

Since I’ve worked here, infanticide has been the outcome every time an infant sired by a male in another group has been born to a newly transferred female.  It’s also happened when there have been interactions between lone silverbacks and family groups.  In that case, the intruding male makes the kill.  I don’t know if anyone will ever understand exactly how a silverback recognizes an infant that doesn’t belong to him.  The Karisoke researchers think the timing of the transfer is the main factor.  If the female is in early pregnancy when she joins a new group, her babies can be born and left alone.  (The same theory holds for chimpanzees.)  It could be that the silverback remembers whether or not he mated with the female.  Maybe she behaves differently in some way toward him, or the infant smells or looks different in some way.  Some trackers have told me they think the silverback kills only male infants, but this one was a female, and other female babies have been killed since I’ve been here.

One thing is certain: clearly the silverback recognizes infants who are not his.  But what about the female?  I can’t help wondering what in the world this new mother of twins was thinking—or not thinking.  It’s hard to believe she didn’t sense the risk of returning to her former group late in pregnancy.  Or maybe she did, but food and protection and other advantages mattered more in her scheme of things.

Shinda eating but moving slowly the day before he disappeared on November 19, 2008.

The day the twins were born and killed ended on an even more negative note.  The Karisoke trackers couldn’t find Shinda, the silverback in charge of the group bearing his name.  We’d been monitoring Shinda for lethargy and decreased appetite.  Magda had just visited him the day before.  He was alert and eating, though slowly, and appeared to be experiencing pain in his back or hips.  We’d made a plan to check him again if he didn’t improve.  When he disappeared, we assumed the worst, though it was true that he’d rebounded from similar episodes of lethargy before.  Perhaps he’d rejoin his family the next day.  Four days later, the trackers found Shinda dead.

Shinda on June 14, 2007 recovering from an acute episode of weakness.

There are three other young silverbacks in the Shinda Group.  When Magda had reported on the silverback the other day, we’d thought the problem might be fighting among the males.  We also thought it might be a repeat of what I’d seen in June 2007, when one of the researchers had found Shinda rolling on the ground as if he’d had a seizure.  By the time I got to him an hour later, he seemed a little dazed and unsteady on his feet, as if in pain; then he started walking and eating, and looked normal a few hours later.  A few months later, he had a weeklong episode of lethargy, but otherwise he appeared normal.  We thought maybe he was suffering from arthritis or an old injury, or possibly heart disease.  We’d checked his stool sample for parasites and hadn’t found any out of the ordinary (most free-living gorillas have some parasites.)

Shinda eating and acting normally the day after an episode of weakness, June 15, 2007.

At thirty-one-and-a-half, Shinda was among the older silverbacks, but not past his prime.  Until he disappeared, the trackers and researchers had reported that he still seemed very much in charge.  We continued to hope for the best, while also discussing what we’d be able to for him if we deduced that he did in fact have either an age-related disease or a chronic injury.  Our-decision making always goes back to whether or not the problem is life threatening—and beyond that, to whether an intervention has a good chance of a positive outcome without disrupting the group.  We figured if Shinda was found alone but alive and in trouble, we’d do what we could.  Sadly, we never had that opportunity.

We found several abnormalities during Shinda’s post mortem exam, but not enough to provide a clear picture of what had killed him.  The final explanation for his death will be determined by expert analysis in the U.S. at the University of California, Davis.  He was dehydrated, and the lining of his stomach was full of bruised and bloody areas—ulcers.  His liver and adrenal glands looked abnormal, too.  We didn’t find evidence of a heart problem or of severe arthritis, though in the absence of an X-ray machine we could exclude these possibilities only by examining each joint and dissecting his spine.  His brain also appeared normal, but firm conclusions on that will have to wait for the microscopic part of the study.  Shinda’s stomach ulcers must have made him feel awful, and they could explain his recurrent episodes of lethargy, but at this stage we cannot know if they were the primary problem, or the result of another one.

Shinda in 2007.

This exam, by the way, took five of us about eight hours.  Shinda weighed at least 200 kilograms (we used our hanging scale to weigh him, but the dial would only go around once.)  We follow a very detailed protocol for taking measurements, weights, and preserving samples.  Our team included Elisabeth, the vet technician from the park service (ORTPN), Magda, Jean Felix, project director Mike (who was here for one of his regular visits), and me.  Jean Paul and I spent the entire next day and part of the weekend doing the lab work.  Even now, we’re still working on the report.  Ultimately, we’re bound to learn something new from the final result, and the information gained will add to our overall understanding of mountain gorilla medicine.

Infants in Amahoro group playing, November 12, 2008.

A few days later, we heard that an infant gorilla in Amahoro Group had been found dead.  This was Umurage, a little female I’d seen playing and looking healthy just two weeks earlier.  Since the trackers reported that there’d been an interaction with a wild group earlier in the week, we think this infant was killed during a fight between gorilla groups.  The results of Umurage’s post mortem were clear: she’d been killed by a blow to her abdomen that ruptured her stomach and one kidney and bruised her intestines.  She also had bruising of one ankle, as if she’d been grabbed by her feet and thrown.  Unfortunately, such incidents are among the realities of life for the mountain gorillas.

To end on a positive note, several babies have been born recently in both the research and tourist groups in Rwanda—including one just the other day—and all are perfectly fine.  The news from DR Congo is also encouraging (see gorilla.cd blog.)  The ICCN provincial director, Emmanuel de Merode, met with rebel leaders in the Mikeno sector of the Virunga Park and reached an agreement.  The ICCN rangers have moved back to their main station at Rumangabo and so far they’ve been able to check on two gorilla groups.  There are five infants!